Re: [PATCH v7 15/19] soc: starfive: Add jh7110-hdmi-subsystem driver

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Medium] soc: starfive: wrong regmap stride and val_bits in
  jh7110-hdmi-subsystem
--

commit 7b3e8ed6b5c2397fee05f3afbf224c172c611228
Author: Michal Wilczynski <m.wilczynski@samsung.com>

soc: starfive: Add jh7110-hdmi-subsystem driver

This commit adds a platform driver for the StarFive JH7110 HDMI subsystem
that initializes a shared MMIO regmap and populates the child HDMI PHY and
controller devices.

> diff --git a/drivers/soc/starfive/jh7110-hdmi-subsystem.c b/drivers/soc/starfive/jh7110-hdmi-subsystem.c
> new file mode 100644
> index 0000000000000..b01dc66450f51
> --- /dev/null
> +++ b/drivers/soc/starfive/jh7110-hdmi-subsystem.c
> @@ -0,0 +1,72 @@
[ ... ]
> +static const struct regmap_config starfive_hdmi_regmap_config = {
> +	.reg_bits = 32,
> +	.val_bits = 8,
> +	.max_register = 0x3fff,
> +};

[Severity: Medium]
Should starfive_hdmi_regmap_config set .val_bits = 32, .reg_stride = 4, and
.max_register = 0x3ffc to match the 4-byte register layout expected by the
child drivers?

Both the HDMI controller and PHY drivers address this shared regmap at
4-byte-strided offsets (offset * 4 and reg * 4), and the controller's own
inno_hdmi_regmap_config uses 32-bit values with a 4-byte stride:

drivers/gpu/drm/bridge/inno-hdmi.c:
	static const struct regmap_config inno_hdmi_regmap_config = {
		.reg_bits = 32,
		.val_bits = 32,
		.reg_stride = 4,
	};

	static inline u8 hdmi_readb(struct inno_hdmi *hdmi, u16 offset)
	{
		u32 val;

		if (regmap_read(hdmi->regmap, offset * 4, &val))
			return 0;

		return val;
	}

With .val_bits = 8 and .reg_stride left at its default of 1, regmap_mmio
uses readb()/writeb() instead of 32-bit MMIO accessors, does not check
4-byte register alignment, and steps through 0x0000..0x3fff byte-by-byte in
regmap debugfs, issuing unaligned byte reads to the upper three bytes of
every 32-bit register word.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261106-jh7110-clean-send-v7-0-68f7ea9913db@samsung.com?part=15